Modeling cumulative evidence for freedom from disease with applications to BSE surveillance trials

This investigation deals with the question of when a particular population can be considered to be disease-free. The motivation is the case of BSE where specific birth cohorts may present distinct disease-free subpopulations. The specific objective is to develop a statistical approach suitable for documenting freedom of disease, in particular, freedom from BSE in birth cohorts. The approach is based upon a geometric waiting time distribution for the occurrence of positive surveillance results and formalizes the relationship between design prevalence, cumulative sample size and statistical power. The simple geometric waiting time model is further modified to account for the diagnostic sensitivity and specificity associated with the detection of disease. This is exemplified for BSE using two different models for the diagnostic sensitivity. The model is furthermore modified in such a way that a set of different values for the design prevalence in the surveillance streams can be accommodated (prevalence heterogeneity) and a general expression for the power function is developed. For illustration, numerical results for BSE suggest that currently (data status September 2004) a birth cohort of Danish cattle born after March 1999 is free from BSE with probability (power) of 0.8746 or 0.8509, depending on the choice of a model for the diagnostic sensitivity.

Evaluation of the cumulative evidence for freedom from BSE in birth cohorts

Substantial resources are used for surveillance of bovine spongiform encephalopathy (BSE) despite an extremely low detection rate, especially in healthy slaughtered cattle. We have developed a method based on the geometric waiting time distribution to establish and update the statistical evidence for BSE-freedom for defined birth cohorts using continued surveillance data. The results suggest that currently (data included till September 2004) a birth cohort of Danish cattle born after March 1999 is free from BSE with probability (power) of 0.8746 or 0.8509, depending on the choice of a model for the diagnostic sensitivity. These results apply to an assumed design prevalence of 1 in 10,000 and account for prevalence heterogeneity. The age-dependent, diagnostic sensitivity for the detection of BSE has been identified as major determinant of the power. The incorporation of heterogeneity was deemed adequate on scientific grounds and led to improved power values. We propose our model as a decision tool for possible future modification of the BSE surveillance and discuss public health and international trade implications.

The "freedom to frame questions... worth asking" or three stories and three (other) fragments of research

In our state of centralised control of the curriculum and high-stakes testing an examination subject's assessment objectives have become high profile. Some of the anomalous effects of this profile are shown in the teaching, question-setting, and marking of English literature. Glimpses of earlier times are revealed, all three secondary school key stages are considered, examination performances are discussed, and the views of beginning teachers about teaching to the test are sought.

Shakespeare and Islam

This special issue conceives of “Shakespeare and Islam” in its broadest sense, conceptually, and opens up the conjunction to consideration of both the early modern and more recent periods. It is not directly concerned with addressing doctrinal questions: “Islam” is a flag of convenience for our purposes, an umbrella term that takes in not only the Ottoman Empire but also the Persian (a subject that, perhaps unsurprisingly, tends to be overshadowed by its stronger neighbour), and extends to a discussion of twentieth- and twenty-first-century issues of Shakespearean interpretation. In line with this journal's principal remit, the essays concentrate on questions of staging and interpretation, adaptation and appropriation, thus drawing on and contributing to one of the dominant fields of Shakespeare studies today. While the early modern period remains the collection's central interest, two concluding essays remind us (if we need reminding) that the seemingly endless recycling and reinterpretation of Shakespeare have implications for how we understand the conjunction with Islam today.